1. Field of the Invention
The present invention relates to an improved reactor suitable for chemical reactions bringing into play fluids in contact with a bed of solids. This is notably the case in reactors lined with a bed of solids traversed by the one or more fluids to be reacted.
2. Description of the Prior Art
Thus for example reactions for the dehydrogenation of hydrocarbons and in particular the manufacture of styrene from ethylbenzene are customarily carried out by passing a superheated mixture of hydrocarbon and steam through a catalyst bed placed inside a cylindrical reactor. In the reactor, the gas circulation can be effected parallel to the axis for the cylinder, the reactor then being called axial, or parallel to the radii of cross sections of the cylinder, the reactor then being called radial. The design of reactors of greater and greater capacity has led to the gradual abandonment of axial reactors in favour of radial reactors.
In radial reactors, the circulation of the gases or other fluids can be carried out either from the middle of the reactor to the periphery, the reactor then being called centrifugal, or from the periphery to the axis of the reactor, the reactor being called in this case centripetal.
Centrifugal reactors are sometimes preferred, since they offer the gases or other fluids a lower pressure drop, which favors the selectivity of the reaction and consequently the yield. However centripetal reactors possess various advantages which may render them preferable to centrifugal reactors: their technological construction is easier; on the other hand, superheated intake fluids are placed in contact with the largest surface of the solid material, which diminishes the risk of fouling and ensures better distribution of the fluids in the solid mass; finally the largest empty space of the reactor which is necessarily the central tube is kept at the lowest temperature.
In radial reactors, a gradual packing of the bed of solid material occurs in the course of its use. To compensate this packing and to maintain correct radial circulation in the reactor, it is necessary to place an excess of solid material in the upper portion of the reactor. It has already been proposed to replace this excess material, at least in part, by an inert substance, but it is then observed that this inert substance penetrates little by little into the whole of the principal bed resulting in poor utilisation of the latter. On the other hand, this upper portion of the bed, whatever its composition, gradually fouls, since it is not swept by the reaction gases or other fluids.
It is an object of the present invention to enable these drawbacks to be overcome by providing a type of reactor with an essentially radial circulation in which the whole of the solid mass is traversed by the reaction gases or other fluids.